The present invention relates generally to shielding screens for preventing radio signal interference between antennas of an integrated antenna system, and in particular to a shielding screen that includes a frequency selective surface that blocks radio frequency signals in a predetermined stop band and transmits radio frequency signals in a predetermined passband.
It is common for an antenna installation to include multiple antennas. Frequently, two or more of the antennas emit radio signals at closely adjacent frequencies, and other antennas emit radio signals at a substantially different frequency. For example, two radar antennas may operate at X-band, and a communication antenna may operate in the UHF band. Heretofore, solid metal plates have been used to shield two X-band antennas from interfering with each other. However, the immediate proximity of this metal plate to a UHF antenna typically causes adverse effects in performance. Such a solid metal plate reflects UHF signals. Such systems are found, for example, in shipboard antenna installations and in various land-based and aircraft-based communications systems wherein the vehicle or topography necessitate integrating multiple antennas in closely adjacent positions.
Therefore a need exists for a shielding screen which can be positioned between two or more antennas of an integrated antenna system that emit signals at closely adjacent frequencies which effectively blocks the signals from one of the antennas from interfering with the signals emitted from the other and which simultaneously transmits signals emitted from other antennas of the integrated antenna system which emit signals at a substantially different frequency.
It is therefore an objective of the invention to provide an improved shielding screen for use in multiple antenna systems. Another objective of the invention is to provide a shielding screen which blocks radio signals in a predetermined stop band and transmits signals in a frequency-displaced pass band. Yet another objective of the invention is to provide a shielding screen which includes a frequency selective surface that is substantially invisible to radio signals in a predetermined pass band and provides adequate attenuation to radio signals in a stop band. Still another objective of the invention is to provide a shielding screen comprised of a multiplicity of conductor elements supported on a thin dielectric substrate, and wherein the conductor elements are configured and dimensioned to reject or reflect radio frequency signals in a stop band and to substantially transmit radio frequency signals in a pass band. Another objective of the invention is to provide a shielding screen which operates effectively when positioned at angles up to 60.degree. with respect to a line normal to the plane of an antenna. Still another objective of the invention is to provide a shielding screen that is easily fabricated, flexible, and low in cost.